shill: Ignore missing-field-initializers warning on LAZY_INSTANCE_INITIALIZER.

When compiling with -Wextra, GCC gives a missing-field-initializers
warning (which is promoted to an error by -Werror) on the
LAZY_INSTANCE_INITIALIZER macro defined in base/lazy_instance.h.

This CL adds -Wno-missing-field-initializers to CXXFLAGS in Makefile to
ignore the warning on LAZY_INSTANCE_INITIALIZER.

BUG=chromium-os:29866
TEST=Build and run unit tests.

Change-Id: I8533f3b89780d1ec2b2c7222be3f5e26aa0e3b83
Reviewed-on: https://gerrit.chromium.org/gerrit/20888
Reviewed-by: Darin Petkov <petkov@chromium.org>
Tested-by: Ben Chan <benchan@chromium.org>
Commit-Ready: Ben Chan <benchan@chromium.org>
diff --git a/resolver.cc b/resolver.cc
index 22632c7..b0bc41c 100644
--- a/resolver.cc
+++ b/resolver.cc
@@ -20,9 +20,9 @@
 
 namespace shill {
 
-// TODO(ers): not using LAZY_INSTANCE_INITIALIZER
-// because of http://crbug.com/114828
-static base::LazyInstance<Resolver> g_resolver = {0, {{0}}};
+namespace {
+base::LazyInstance<Resolver> g_resolver = LAZY_INSTANCE_INITIALIZER;
+}  // namespace
 
 Resolver::Resolver() {}